Update on posterior cortical atrophy

Abstract

Purpose of review: Non-amnestic (or atypical) presentations of neurodegenerative dementias are under-recognized and under-diagnosed, including posterior cortical atrophy (PCA) syndrome, which is characterized by prominent visuospatial and visuoperceptual dysfunction at presentation. It is most commonly due to Alzheimer's disease (AD) pathology, while Lewy body disease, corticobasal degeneration, and prion disease are pathologies less frequently associated with PCA. The diagnosis of PCA is often delayed, to the detriment of the patient, and awareness and understanding of PCA will improve detection, prognostication, and treatment. Recent findings:The natural history of PCA appears to be distinct from typical AD and significant heterogeneity exists within the PCA syndrome, with the underlying causes of this heterogeneity beginning to be explored. Functional and molecular imaging can assist in better understanding PCA, particularly assessment of network disruptions that contribute to clinical phenotypes. CSF biomarkers are useful to detect underlying pathology, but measures of retinal thickness are less promising. There are currently no adequate treatment options for PCA.Summary: Continued efforts to characterize PCA are needed, and greater awareness and understanding of atypical presentations of neurodegenerative dementias could serve to elucidate pathobiological mechanisms of underlying disease.

Visuospatial working memory dysfunction from tapping span test as a diagnostic tool for patients with mild posterior cortical atrophy

“…Still, we consider that the usefulness of the simple tapping span test in clinical settings is remarkable. In addition, visuospatial working memory dysfunction, which is easily evaluated with the tapping span test, might be a hallmark of posterior cortical atrophy as is phonological working memory dysfunction (verbal repetition deficits) in logopenic variant primary progressive aphasia, both of which constitute atypical presentation of Alzheimer’s disease 2 , 3 , 15 . These working memory dysfunctions we discussed in this article belong to short-term memories rather than those related to executive functions, which is associated with frontal cortex 35 but not posterior cortex.…”

“…Patients with > 1 on clinical dementia rating were excluded because the aim of this study was to examine whether the tapping span test is a potential diagnostic tool for mild posterior cortical atrophy. Among 13 patients who met both the clinical and imaging-supported diagnostic criteria for posterior cortical atrophy 2 , eight individuals who were in the mild form, that is, with a clinical dementia rating of 0.5 18 , were recruited. Time period from onset of first symptoms to inspection day was 2.8 ± 1.7 years (range: 0 to 5 years).…”

“…Posterior cortical atrophy is a rare degenerative condition which commonly occurs between ages 50 and 65 and is characterized mainly by visuospatial dysfunction 1 , 2 . This condition is under-recognized and underdiagnosed 1 – 3 because a diagnosis of posterior cortical atrophy is sometimes challenging among assessments of neurodegenerative conditions 3 , in particular, of the mild form and can be delayed not only because of the rarity of this condition but also because, aside from visuospatial dysfunction, patients with mild posterior cortical atrophy function almost normally with respect to memory, language, and behavior and maintain a relatively preserved motivation and insight 3 – 7 .…”

“…Visuospatial dysfunction is the most common feature for mild posterior cortical atrophy 2 . Based on a neuropsychological examination for visuospatial dysfunction, visuospatial working memory was found to be impaired for patients with posterior cortical atrophy when compared with those with amnesic Alzheimer’s disease 9 – 11 .…”

Tapping Span Test as a Simple Diagnostic Tool for Patients With Initial-stage Posterior Cortical Atrophy: Short Tapping Span Length Indicates Visuospatial Working Memory Dysfunction

“…Posterior cortical atrophy is a rare degenerative condition which commonly occurs between ages 50 and 65 and is characterized mainly by visuospatial dysfunction 1,2 . This condition is under-recognized and underdiagnosed 1 because a diagnosis of posterior cortical atrophy is sometimes challenging among assessments of neurodegenerative conditions, in particular, in the initial stages and can be delayed not only because of the rarity of this condition but also because, aside from visuospatial dysfunction, patients with initial-stage posterior cortical atrophy function almost normally with respect to memory, language, and behavior and maintain a relatively preserved motivation and insight [3][4][5][6] . In addition, typical simple neuropsychological tests, e.g., Mini-Mental State Examination (MMSE) 7 , do not focus on symptoms of this condition; rather, their goal is mainly to assess orientation, calculation, repetition, and memory functions.…”